Interactions between Iron and other Metals

It would be surprising to find that there were no interactions between iron and a number of other divalent transition-metal ions in mammalian systems, not least... 

As introduced above, the interaction between the hydrosphere and the lithosphere frequently results in mass exchange. In this way rocks get dissolved, sediments build-up, stalactites and stalagmites form, materials get transported, and so on. The pH of water and of sediments determines the mobility and solubility of different elements, which may in turn modify the redox potential of the aqueous medium. For example, aluminum, calcium, magnesium, iron, manganese, and other metals become more soluble at low pH if pH increases, their solubility decreases and precipitation occurs. 

In l,3-dichalcogena-[3]ferrocenophanes of the type fc(E2M) (E = O, S, Se, Te), a transition metal complex fragment (M) is held firmly between the two chalcogen atoms (E) (Table 5-5). Although both the ferrocene iron and the transition metal are essential parts of the cyclic structure, the two metals generally remain isolated from each other. Only a few examples have been found where an intramolecular, transannular interaction between Fe and M can be taken into consideration, as in the palladium(ii) and platinum(ii) complexes fc[E2M(PPh3)] (E = O, M = Pd E = S, M = Pd and Pt) (Sect. 5.7.1). 

The appreciation of H2 complexes was delayed by the notion that such complexes could not be stable relative to classical dihydrides. Even the theoretical basis for interaction of H2 and other o-bonds with a metal was still undeveloped at the time of the initial discovery. Ironically, a computational paper by Saillard and Hoffmann7 in 1984 on the bonding of H2 and CH4 to metal fragments such as Cr(CO)s was published only shortly after our publication of the W-H2 complex (without mutual knowledge). Such interplay between theory and experiment has continued to be an extremely valuable synergistic relationship.3,4,8 The innate simplicity of H2 was attractive computationally, but the structure/bonding/dynamics of H2 complexes turned out to be extremely complex and led to extensive study (>300 computational papers). 

The use of CPs as anticorrosion materials has several advantages. CPs are suitable to replace chromate and other hazardous materials. They are cheap and easily deposited on protecting substrate by electrochemical or chemical synthesis methods. Moreover, CPs have the equilibrium potential positive relative to those of iron, aluminium and some other metals, so they can protect effectively ferrous and non-ferrous alloys. Although these beneficial properties, the interactions between CP and metal are numerous and complex, and the mechanisms of the corrosion protection are not yet fully clarified. 

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